Biofluids (e.g., complex mixtures such as blood, saliva, or urine) are routinely separated using chromatography before the MS measurement in order to minimize suppression effects on analyte ionization and to pre-concentrate the analytes. Recently, systems and methods have been developed that allow for sample preparation and pre-treatment to be combined with the ionization process (See Ouyang et al., WO 2010/127059).
These systems and methods use wetted porous material, named paper spray ionization, for direct, qualitative and quantitative analysis of complex biofluids (“paper spray”). Analyte transport is achieved by wicking in a porous material with a macroscopically sharp point and a high electric field is used to perform ionization and chemical analysis of compounds present in biological samples. Pneumatic assistance is not required to transport the analyte: a voltage is simply applied to the wet paper, held in front of a mass spectrometer.